The present invention relates to a device for fixing a sheet (map film) for use in an information display unit adapted to display the present position of an automobile on the map film by means of a spot of light which moves along the course of movement of an automobile.
An automobile position display unit developed recently has a cathode ray tube on the surface of which a map film is placed so that the light spot on the cathode ray tube is moved on the map film to inform the driver of the present position of the automobile. More specifically, in this automobile position display unit, the course and running distance of the automobile are calculated by a microcomputer from data concerning the running distance and direction derived from a rotation detector associated with the wheel of the automobile and a direction detector such as a gyro-compass, and the light spot on the cathode ray tube is moved along the running course of the automobile in accordance with the output from the microcomputer.
The map film used in this automobile position display unit is a transparent plastic film on which the map is printed. This map film, when used, is clamped and fixed between the display surface of the cathode ray tube and the front surface cover of the display device.
Hitherto, various types of devices have been proposed for fixing the map film or sheet. These devices, however, could not stably hold the map film or sheet in correct position against vibration to which the map film or sheet is subjected during running of the automobile, as will be fully explained later with reference to the drawings.